Elastomeric polyester-derived polyurethanes containing 12-hydroxymethyl-tetrahydroabietanol

ABSTRACT

Ethylene glycol adipic acid polyester was modified by incorporating the naval stored derived 12-hydroxymethyltetrahydroabietanol in the polyester chain. The modified polyester was blended with a poly (ethylene adipate) glycol (mol. wt. 2000) and 1,4-butanedio, Bu(OH)2, giving glycol mixtures which were reacted with toluene diisocyanate TD1. Clear strong polyurethane films (26.6 percent TD1) from glycol mixtures (average hydroxyl equivalents, OHE, of 252) containing 5, 10, 15 and 20 percent resinyl moiety were prepared and their polymer properties examined. Incorporation of the moiety gave strength, toughness, and stiffness to films which otherwise would have been soft and tacky. Glycol mixtures having higher hydroxyl equivalents values required less isocyanate and addition of the resinyl glycol gave strong elastic cilms from a composition containing 16.6 percent TD1. Experimental data suggests that use of the bulky 12hydroxymethyltetrahydroabietanol may be an important contribution to polyurethane technology.

United States Patent 91 Lewis et al.

[ 51 Jan. 2, 1973 [75 l lnventorsz John B. Lewis, Glen W. Fredric k,

both of Lake City, Fla.

I Agriculture 22 Filed: Dec. 16,1971 [21] Appl. No.: 208,935

Related U.S. Application Data [62] Division of Ser. No. 36,673, May 12, 1970, Pat. No. v

3,432,451 3/l969 Kales ..260/27 R Assignee: The United States of America g represented by the Secretary of Primary Examiner-Donald E. Czaja Assistant Examiner-William E. Parker Attorney-R. Hoffman et al.

[5 7] ABSTRACT Ethylene glycol adipic acid polyester was modified by incorporating the naval stored derived 12-hydroxymethyltetra-hydroabietanol in the polyester chain. The modified polyester was blended with a poly (ethylene adipate) glycol (mol. wt. 2000) and 1,4-butanedio, Bu(OH),, giving glycol mixtures which were reacted with toluene diisocyanate TDl. Clear strong polyurethane films (26.6 percent TDl) from glycol mixtures (average hydroxyl equivalents, OHE, of 252) containing 5, 1O, 15 and 20 percent resinyl moiety were prepared and their polymer properties examined. Incorporation of the moiety gave strength, toughness, and stiffness to films which otherwise would have been soft and tacky. Glycol mixtures having higher hydroxyl equivalents values required less isocyanate and addition of the resinyl glycol gave strong elastic cilms from a composition containing 16.6 percent TDl.

Experimental data suggests that use of the bulky 12- hydroxymethyltetrahydroabietanol may be an important contribution to polyurethane technology.

1 Claim, No Drawings onto-" onion O CHzOiIkCHzM OCQHJOH For the past few years a study to develop new markets for rosin has been underway to make poly-functional derivatives of resin acid and rosin by introduction of hydroxymethyl groups. Parkin and Hedrick [G.

and Hedrick [1&EC, Prod. Res. & Dev., Vol. 9, page 304 (1970)] describe polyurethanes made from Org. Chem., 30, 2356 (1965)] and Parkin et al. [1&EC,

Prod. Res. & Dev., 5, 257 1966)] describe the reaction of levopimaric acid with formaldehyde. The adduct resulting from this reaction is readily converted to the diol, l2-hydroxymethyltetrahydroabietanol (I).

Pine oleoresin (pine gum), the exudate from the living pine tree, contains from 18 to 25 I percent levopimaric acid, and since itsreaction in situ in gum with formaldehyde is essentially quantitative, gum might be considered an economical source for the abietanol derivative. The glycol is easy to obtain pure. Initial experiments to use it in polyurethanes demonstrated problems resulting from insolubility charac-' teristics and melting point of 183 C. This invention shows the results of incorporating the hydroxymethylabietanol derivative in hydroxyl-terminated polyglycol adipates to overcome the adverse physical properties and then use of the modified glycol adipates in polyurethane elastomers.

Polyester urethane thermoplastic polymers are becoming more popular industrially because of the unique properties obtainable by changes in formulations which result in markets formerly filled by use of one or more old line plastics. v

A study was undertaken to determine the effectthe bulky resinyl moiety-had on the properties of polyesterpolypropylene glycols modified by incorporating the resinyl moieties II and III in the polyether chain.

To evaluate the resinyl glycol (l), the glycol was reacted with two mole equivalents of adipic acid and the resulting adipate was heated with excess'ethylene glycol until the acid value indicated the acid has all reacted. This glycol was then blended with poly(ethylene adipate) glycol (OI-IE, approximately 1,000) and l,4-butanediol and the glycol blend reacted with diisocyanate. In the first experiments TDI was used and since the results were meaningful and perhaps unusual, this isocyanate was used throughout to prepared polymers in a one-step process.

The preparation of the glycol (IV) was surprisingly easy and competitive reactions from transesterification were of little consequence. Conversion of l2-hydroxyrnethyltetra-hydroabietanol to IV eliminated the problem resulting from its low solubility and high melting point. Glycol (IV) was easily mixed with other glycols used in the experiments reported. No attempt was made to prepare higher molecular weight esters of I. Mixed ethylene glycol adipic acidv esters of 12 hydroxymethyltetrahydroabietic acid could not be made without considerable ester interchange. The same was true of the ethylene glycol ester of this acid .Early workers concluded the optimum molecular weight of the poly (ethylene adipate) glycol was 2,000, and also report data showing that 1,4-butanediol was probably superior to other commercially available aliphatic diols when used as an extender.

Early workers reacted the poly (ethylene adipate) glycol with excess 4,4-diphenylmethyl diisocyanate to obtain an isocyanate-terminated polyurethane which was reacted with the extender to produce high molecular weight (30 to 50,000) polyurethanes. Early experi-' ments with resinyl glycols, employing a two-stop process using butanediol as an extender gave polymers ,having tensile properties almost identical to those obtained using a one-step process. It was concluded that thecombined effects of TDI and the resinyl moiety masked the differences resulting from a two step preparation.

In the present invention, polyurethanes from TDI and a mixture of poly (ethylene adipate) glycol (mol. wt., 2000) and butanediol were soft and weak with an average hydroxyl equivalent of the glycol mixture of about 250. An incorporation of 5 percent of the resinyl material (III) in the formulation had a marked increase in the tensile properties. Additional increases of l0, l5, and 20 percent resulted in films having increased strength and stiffness (Items 1 to 4, Table l) and at 25 percent the hot polymer mixture was too viscous to handle and was hard and brittle cold. The average OHE of the glycol mixture in this series was held at 252 and the maximum variance in resinyl composition with this OHE value was from 5 to 20 percent becauseof the elastic properties of the film. The resinyl compound (III) requirementwas less for polyurethanes made from glycol mixtures with lower average molecular weights.-

molecular weight of the mixture was increased (Item 5, Table I). Since the NCOzOI-l ratio was in each case 1.05:1, an increase in molecular weight called for less isocyanate.

The literature references above state that aromatic 5 rings phenyl or naphthalene and branching of methyl groups have the effect on modulus.

Pigott et al. [J. Chem. Eng. Data 5, 391 (1900)] state that because of increased bulkiness and rigidity of naphthalene diisocyanate when compared with p-phenylene diisocyanate in urethanes, substantial increases in hardness and 300% modulus were noted. When TDI was compared with p-phenylene diisocyanate the effect of the reduced symmetry combined with the methyl 15 substituents was demonstrated by a general decrease in tensile, modulus, tear, and hardness. When comparing polyester glycols, the tensile and modulus of the elastomers made from a polyester containing methyl side chains were significantly lower than for the elastomers prepared from linear polyesters.

moles) were heated to l90-200 C while sparging with a slow stream of nitrogen until water of the reaction had all distilled. The product was a colorless, low-melting solid, 576 g; calcd; 578 g.

Anal. calcd for C rl N.E., 288.2. Found: N.E.,294.

Ethylene Ethylene glycol (186 g; 3 moles) was added and heating (195 C.) resumed while slowly sparging with nitrogen. After 2% hours [acid number (A.N.) 9]

0 ethylene glycol (31 g; 0.5 mole) was added and the .2 NH, TABLE I.POLYURETIIANE FILMS FROM POLYESTER (1V) Durom- Cone. Taber eter Polyof III loly Ave. llritabrasion Shore estcr in (ethylene 011E Tensile Modulus, p.s.i. Elongatlc Stifiwt. loss, "A" (1V) film, Bl1(O.l1)z adipate) glycol strength, tion, point, ness percent hard- Item equiv. percent equiv. equiv. mix p.s.i. 100% 200% 300% Percent 0. T1, C. 10- ness 1 fl 0508 0. 341 0. 0873 252 3, 524 220 311 382 502 25 7. 0 0. 56 65 u 112 0.305 0. 0715 252 5, 774 247 328 442 570 27 --0. 5 1. 24 70 a 153 0. 27 0. 0550 252 (S, 067 447 740 1, 548 +7. 0 206 0. 235 0. 0398 252 8, 532 1, 2111 2, 148 4, 415 0 l 258 0. 0454 455 4, 554 285 385 550 0 6 'L; 0.20 0. 100 340 4, 600 350 7 250' 4, 300 360 OHE, 343. Technology, 10, 197 (1960)]; Table 2 Poly (tetramethylene adipate) b OHE, 358; TDI equiv. for (1) through (4) inc. 0.50; for (5), 0.313; NCOzOH ratio equiv 1.05:1. Taken from bench marks. 4 Pigott et a1. (1963), Table I; TDI, .32 equiv.; NCOzOH ratio, 1.07:1, Shore B hardness. Schollenberger [Polyurethane At this time the reasons for the effect of incorporating the glycol (I) in the polyurethane chain is not clear. The resinyl group is far more bulky and has a greater number of alkyl substituents than materials heretofore investigated. The bulkiness should result in an increase in modulus which is demonstrated by date in Table 1. Based on published data above, the lack of symmetry and the presence of the alkyl substituents combined 4 with the effects of TDI in the polymers should have resulted in films with reduced strength. This was not the case.

The increase in strength resulting from addition of I may result from entanglement; however, evidence against this is the complete recovery of specimens after stretching almost to the breaking point. The recovery rate, however, decreases with increase in incorporation ifI.

EXAMPLE 1 l-lydroxyl-terminated Hydroxymethylabietanyl Adipate (IV). 12-l-lydroxymethyltetrahydroabietanol (1) (322.5 g; 1.0 mole) and adipic acid (292 g; 2.0

gggcol, 0.2 equiv.; 1,4-bis (Z-hydroxymethoxy) benzene, 0.3 equiv.; TDI, equiv.

EXAMPLE 2 Polymer Preparation. For polymer preparation, experience dictated that the average hydroxyl equivalent (OHE) of the glycol blend should be approximately 250. A typical film preparation is as follows. A poly (ethylene adipate) glycol 88.28 g (OHE, 1030), was heated to 100 C. at 0.2 mm for min., and glycol removed leaving 87.28 g in the flask (Item 1, Table I).

Glycol IV was added, heated to 100 C. for 15 min., degassed at 0.2 mm, and then butanediol added, mixed,

and degassed at 100 C. at mm. After cooling to C., the TDI was added, mixed at atmospheric pressure, then heated to C. at 0.2 mm. pressure until mixing was complete. Some cooling by a water bath was required. The clear liquid polymer mixture was poured hot into.molds which consisted of a 6 inch X 6 inch (inside) aluminum metal frame clamped to a inch thick aluminum sheet covered with thin aluminum foil. The metal frames and plate were enclosed in a galvanized, steel, square box covered with plywood which supported a thermometer. The plates were maintained at -1 10 C. by a hot plate. The reaction mixture was poured onto the foil in an amount (about42 g) so that approximately l/16-inch thick films resulted. Eighteen hours at 100-l 10 C. was required for curing.

The films were cut to remove them from the frames, immersed in dilute mineral acid to dissolve the foil, and washed, then exposed to the atmosphere about one week on the laboratory bench.

Tensile properties of the clear, almost colorless films were run at the Naval Stores Laboratory and other tests were made by commercial laboratories.

with about 0.0398 to about 0.0873 equivalents of poly (ethylene adipate) glycol at a temperature of about 100 C. for a period of about 15 minutes,

b. degassing the mixture from (a) at about 0.2 mm

pressure,

0. adding to the mixture from (b) about 0.235 to about 0.341 equivalents of 1,4 butanediol,

d. degassing the mixture from (c) at a pressure of about 35 mm Hg and a temperature ofabout 100 C.,

e. cooling the mixture from (d) to about 60 C. and adding about 0.313 to about 0.50 equivalents of toluene diisocyanate, and

f. heating the mixture from (c) to a temperature of about C. and at a pressure of about 2 mm Hg until mixing is complete. 

